Re: [Qemu-devel] [PATCH v6 5/7] hw/core: rebase sysbus_get_fw_dev_path() to g_strdup_printf()

[Michael S. Tsirkin]

On Wed, Jun 17, 2015 at 02:45:03PM +0200, Laszlo Ersek wrote:
> This is done mainly for improving readability, and in preparation for the
> next patch, but Markus pointed out another bonus for the string being
> returned:
> 
> "No arbitrary length limit. Before the patch, it's 39 characters, and the
> code breaks catastrophically when qdev_fw_name() is longer: the second
> snprintf() is called with its first argument pointing beyond path[], and
> its second argument underflowing to a huge size."
> 
> Cc: Markus Armbruster <address@hidden>
> Cc: Marcel Apfelbaum <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Laszlo Ersek <address@hidden>
> Tested-by: Marcel Apfelbaum <address@hidden>
> Reviewed-by: Marcel Apfelbaum <address@hidden>
> Reviewed-by: Markus Armbruster <address@hidden>

Reviewed-by: Michael S. Tsirkin <address@hidden>

In fact, I'd Cc stable on this one.

> ---
> 
> Notes:
>     v6:
>     - no changes
>     
>     v5:
>     - separate "%s@" from TARGET_FMT_plx with a space [Markus]
>     - copied Markus's note about "no arbitrary length limit" on the retval
>       into the commit message
>     
>     v4:
>     - unchanged
>     
>     v3:
>     - new in v3
> 
>  hw/core/sysbus.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
> index b53c351..92eced9 100644
> --- a/hw/core/sysbus.c
> +++ b/hw/core/sysbus.c
> @@ -281,19 +281,15 @@ static void sysbus_dev_print(Monitor *mon, DeviceState 
> *dev, int indent)
>  static char *sysbus_get_fw_dev_path(DeviceState *dev)
>  {
>      SysBusDevice *s = SYS_BUS_DEVICE(dev);
> -    char path[40];
> -    int off;
> -
> -    off = snprintf(path, sizeof(path), "%s", qdev_fw_name(dev));
>  
>      if (s->num_mmio) {
> -        snprintf(path + off, sizeof(path) - off, "@"TARGET_FMT_plx,
> -                 s->mmio[0].addr);
> -    } else if (s->num_pio) {
> -        snprintf(path + off, sizeof(path) - off, "@i%04x", s->pio[0]);
> +        return g_strdup_printf("%s@" TARGET_FMT_plx, qdev_fw_name(dev),
> +                               s->mmio[0].addr);
>      }
> -
> -    return g_strdup(path);
> +    if (s->num_pio) {
> +        return g_strdup_printf("address@hidden", qdev_fw_name(dev), 
> s->pio[0]);
> +    }
> +    return g_strdup(qdev_fw_name(dev));
>  }
>  
>  void sysbus_add_io(SysBusDevice *dev, hwaddr addr,
> -- 
> 1.8.3.1
>